The downsizing and higher-level integration of electrical and electronic equipment has been accompanied by pronounced heat emission from the mounted electrical and electronic parts and by temperature elevation of the operating environment, such that demand for improvement in the dissipation of heat from the constituent components has been on the rise. For heat dissipation in automotive member and high-power LEDs especially, components composed of metals and ceramics of high thermal conductivity are currently used. In a conventional automotive LED lamp heat sink that is one of the heat-dissipating components, general-purpose resins, or metals having a high thermal conductivity, such as aluminum, are used. In the case of general-purpose plastics, however, the thermal conductivity is low, prohibiting sufficiently cooling the LED module. And in the case of metals such as aluminum, with the specific gravity being large, post processing steps are required in order to enhance the heat dissipation properties. In addition, on account of the metals being manufactured by die casting or extrusion molding, there have been issues including low degrees of freedom in shape, high manufacturing costs, and poor die durability. For this reason, a resin material that has high thermal conductivity, lightened weight, and superior molding workability, and that can be manufactured at low cost has been sought.
As a way of imparting thermal conductivity to a resin, a technique of adding a filer of high thermal conductivity, such as graphite, has been disclosed.
In Patent Document 1, a resin composition excelling in thermal conductivity by adding specific graphite particles having an aspect ratio of 10 to 20, a weight-average particle size of 10 to 200 μm, and a fixed carbon content of 98 mass % or more to a thermoplastic resin is disclosed.
Patent Document 2 discloses an electro conductive resin composition including a thermoplastic resin and graphite powder in which the aspect ratio of 70% or more of the particles is three or less.
Patent Document 3 discloses an LED lamp heat sink in which a thermally conductive resin containing a thermoplastic resin and one or more fillers selected from metals, inorganic substances, carbon fibers, and graphite, is combined with either a metal or carbon material of high thermal conductivity. The technologies described above, however, require dense charging with graphite or other fillers in order to impart thermal conductivity, and thus have had issues of the fluidity being extremely degraded and, depending on the situation, molding proving difficult. What is more, regarding automotive LED lamp heat sinks application, the lamp lens not clouding when exposed to high temperatures is given as a required physical property, and anti-fogging properties are demanded, yet these points are not discussed in the above-noted patent documents at all. Nor is there discussion of ultrasonic weldability in compositing a metal or plastic base material with a thermally conductive resin.